The world-wide variation in the incidence of colon cancer and the increased incidence found in migrants from low to high risk areas support the notion that environmental factors are involved in the etiology of this disease. Furthermore, it has been hypothesized that intestinal bacteria may be generating co-carcinogens from bile acid substrates. The overall objective of this proposed research is to delineate the role of bile acids and the intestinal microflora in colon cancer carcinogenesis. The initial goal will be to determine the concentration of chemical mutagens (carcinogens) in extracted feces taken from individuals with different levels of 7-alpha-dehydroxylase activity. Moreover, beta-glucuronidase beta-glu), azoreductase (Azr), and nitroreductase (nr) specific activities will be determined spectrophotometrically in fecal extracts prepared from different individuals. The second goal will be to determine radiochromatographically the distribution of 7-alpha-dehydroxylase in different intestinal bacteria. The final goal will be to purify and characterize by conventional biochemical techniques 7-alpha-dehydroxylase from Clostridium leptum.